WO2013077430A1 - Euvリソグラフィ用反射型マスクブランクおよびその製造方法 - Google Patents
Euvリソグラフィ用反射型マスクブランクおよびその製造方法 Download PDFInfo
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- WO2013077430A1 WO2013077430A1 PCT/JP2012/080380 JP2012080380W WO2013077430A1 WO 2013077430 A1 WO2013077430 A1 WO 2013077430A1 JP 2012080380 W JP2012080380 W JP 2012080380W WO 2013077430 A1 WO2013077430 A1 WO 2013077430A1
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
- H01L21/0271—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers
- H01L21/0273—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers characterised by the treatment of photoresist layers
- H01L21/0274—Photolithographic processes
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/22—Masks or mask blanks for imaging by radiation of 100nm or shorter wavelength, e.g. X-ray masks, extreme ultraviolet [EUV] masks; Preparation thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/22—Masks or mask blanks for imaging by radiation of 100nm or shorter wavelength, e.g. X-ray masks, extreme ultraviolet [EUV] masks; Preparation thereof
- G03F1/24—Reflection masks; Preparation thereof
Definitions
- the present invention refers to a reflective mask blank for EUV (Extreme Ultraviolet) lithography (hereinafter, referred to as “reflective mask blank for EUV lithography” used in semiconductor manufacturing, etc., simply as “EUV mask blank”. And the manufacturing method thereof.
- EUV Extraviolet
- a photolithography method using visible light or ultraviolet light has been used as a technique for transferring a fine pattern necessary for forming an integrated circuit having a fine pattern on a silicon substrate or the like.
- the limits of conventional photolithography methods have been approached.
- the resolution limit of the pattern is about 1 ⁇ 2 of the exposure wavelength, and it is said that the immersion wavelength is about 1 ⁇ 4 of the exposure wavelength, and the immersion of ArF laser (193 nm) is used. Even if the method is used, the limit of about 45 nm is expected.
- EUV lithography As an exposure technique using a wavelength shorter than 45 nm, EUV lithography (hereinafter referred to as “EUV lithography” in the present specification is also simply referred to as “EUVL”), which is an exposure technique using EUV light having a wavelength shorter than that of an ArF laser. .) Is promising.
- EUV light refers to light having a wavelength in the soft X-ray region or vacuum ultraviolet region, and specifically refers to light having a wavelength of about 10 to 20 nm, particularly about 13.5 nm ⁇ 0.3 nm.
- EUV light is easily absorbed by any substance, and the refractive index of the substance is close to 1 at this wavelength, so that a conventional refractive optical system such as photolithography using visible light or ultraviolet light cannot be used.
- a reflective optical system that is, a reflective photomask and a mirror are used.
- the mask blank is a laminated body before patterning used for photomask manufacturing.
- a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed in this order on a glass substrate or the like.
- a multilayer reflective film is generally used in which a low-refractive index film and a high-refractive index film are alternately laminated to increase the light reflectivity when the EUV light is irradiated onto the surface of the layer.
- a molybdenum (Mo) layer is usually used
- a silicon (Si) layer is usually used.
- the absorber layer a material having a high absorption coefficient for EUV light, specifically, a material mainly composed of chromium (Cr) or tantalum (Ta) is used.
- a multilayer reflective film When a multilayer reflective film is used as a reflective layer of an EUV mask blank, it is necessary to increase the film density of each layer of the multilayer reflective film in order to increase the light reflectivity during EUV light irradiation.
- High film stress ie high compressive stress
- the substrate When such a high film stress is applied to the substrate, the substrate may be deformed. Since a substrate made of a low expansion glass is usually used as a substrate for an EUV mask blank, the deformation of the substrate caused by the application of film stress is minor and thus has not been a problem in the past.
- Patent Document 1 describes that such a change in film stress is caused by very slight mixing of each layer interface constituting the multilayer reflective film.
- This change is at a level that cannot be detected by the periodic length measurement by the X-ray reflectance film thickness measurement, but by this, the peak wavelength of the reflectance of the multilayer reflective film (that is, the reflectance peak of the multilayer reflective film is the maximum).
- (Wavelength) changes at a level of 0.01 nm. Since EUV light has a very short wavelength, it is said that a change in the state of the multilayer reflective film very sensitively affects its wavelength characteristics and reflection characteristics. In addition, since EUV lithography uses light in a specific narrow wavelength band, the influence of wavelength shift is large, and the shift of the peak wavelength of reflectance causes a mismatch with the mirror of the exposure machine used during pattern transfer. Therefore, the peak wavelength must be accurately controlled. Furthermore, the reflectance of the multilayer reflective film is lowered due to the shift of the peak wavelength. As described above, the temporal change in the stress of the multilayer reflective film causes various problems in practical use of the mask, such as a change in the flatness of the substrate.
- Patent Document 1 in order to solve the above-described problems, a heat treatment is performed on the substrate with the multilayer reflective film during and / or after the multilayer reflective film is formed. Thereby, by suppressing the progress of mixing at the interface of each layer constituting the multilayer reflective film, it is possible to suppress the time-dependent change in stress of the multilayer reflective film after film formation, and thereby the multilayer reflective film with respect to EUV light as exposure light It is possible to prevent changes in the wavelength characteristics and reflection characteristics.
- the peak wavelength and the reflectance of the multilayer reflective film are measured before and after the heat treatment, and the change in the peak wavelength and the decrease in the reflectance due to the difference between each peak wavelength and the reflectance are reflected by the reflection of the pattern transfer device.
- Patent Document 1 As an effect of heat treatment, attention is paid only to the suppression of the change in stress of the multilayer reflective film over time.
- the multilayer reflective film Due to the progress of structural relaxation of each layer constituting the multilayer reflective film and mixing of the interface, the multilayer reflective film It is considered that each layer constituting the material shrinks. And it is thought that the film
- each layer constituting the multilayer reflective film contracts and the film stress is relaxed by the structural relaxation of each layer constituting the multilayer reflective film and the progress of mixing at the interface.
- the film stress is relaxed by structural relaxation and mixing.
- the film stress is relaxed by the structural relaxation and mixing in the multilayer reflective film by the heat treatment, depending on the conditions of the heat treatment, the reflection characteristics change during the EUV light irradiation to the extent that the desired value is not satisfied. It may also be caused.
- each layer of the multilayer reflective film contracts greatly in the thickness direction of the layer, and the reflection characteristics during EUV light irradiation, that is, the peak wavelength of the reflected light and the reflection There is a risk that the rate will decrease.
- the surface of the multilayer reflective film is oxidized during the heat treatment, thereby inhibiting the effects of the above-described heat treatment, that is, the relaxation of the film stress due to structural relaxation and mixing in the multilayer reflective film. .
- the uppermost layer of the Mo / Si multilayer reflective film is preferably a Si film in order to prevent oxidation of the multilayer reflective film surface.
- the film stress (that is, compressive stress) of the Si film increases.
- a protective layer may be formed on the Mo / Si multilayer reflective film for the purpose of protecting the Mo / Si multilayer reflective film when forming a pattern on the absorber layer.
- the protective layer formed for such a purpose include a Ru film and a Ru compound (for example, RuB film). Even when the protective layer is formed on the Mo / Si multilayer reflective film, the uppermost layer of the Mo / Si multilayer reflective film is preferably a Si film.
- the Si film which is the uppermost layer of the Mo / Si multilayer reflective film
- the optical constant thereof may change, and the reflection characteristics during EUV light irradiation may change. Specifically, the reflectance of reflected light may be reduced.
- the optical constants thereof are changed by the oxidation of the Ru film or Ru compound film, and EUV light irradiation is performed. There is a possibility that the reflection characteristic at the time changes. Specifically, the reflectance of reflected light may be reduced.
- the present invention can relieve the deformation of the substrate due to the film stress in the Mo / Si multilayer reflective film and can also reduce the temporal change of the film stress in the Mo / Si multilayer reflective film. It is an object of the present invention to provide an EUV mask blank according to the manufacturing method.
- the present invention provides a film forming surface of a substrate (hereinafter referred to as a main surface on the side where a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed. Also, a main surface opposite to the film formation surface is also referred to as a “back surface”), and a multilayer reflection film that reflects EUV light is formed on the multilayer reflection film.
- a method for producing a reflective mask blank for EUVL wherein a reflective mask blank for EUV lithography (EUVL) is produced by forming an absorber layer that absorbs EUV light,
- the multilayer reflective film is a Mo / Si multilayer reflective film, and the uppermost layer of the Mo / Si multilayer reflective film is a Si film;
- a method for producing a reflective mask blank for EUVL wherein after forming the absorber layer, the substrate on which the absorber layer is formed is heat-treated at a temperature of 110 to 170 ° C., preferably 120 to 160 ° C.
- a multilayer reflective film that reflects EUV light is formed on a film formation surface of a substrate, and then an absorber layer that absorbs EUV light is formed on the multilayer reflective film.
- a method for manufacturing a reflective mask blank for EUVL wherein a reflective mask blank for EUV lithography (EUVL) is manufactured by forming a low reflective layer in inspection light used for inspection of a mask pattern,
- the multilayer reflective film is a Mo / Si multilayer reflective film, and the uppermost layer of the Mo / Si multilayer reflective film is a Si film;
- a method for producing a reflective mask blank for EUVL wherein after the formation of the low reflection layer, the substrate on which the low reflection layer is formed is heat-treated at a temperature of 110 to 170 ° C., preferably 120 to 160 ° C.
- a protective layer of the multilayer reflective film is formed on the multilayer reflective film, and after the absorber layer is formed, the absorber
- the substrate on which the layer is formed is preferably subjected to the heat treatment described above.
- a protective layer of the multilayer reflective film is formed on the multilayer reflective film, and the absorber layer is formed on the protective layer
- the low reflective layer is formed on the absorber layer, and after the low reflective layer is formed, the substrate on which the low reflective layer is formed is subjected to the heat treatment described above.
- the protective layer is preferably a Ru layer or a Ru compound layer.
- the heat treatment is performed in an air atmosphere.
- the absorber layer is a layer containing tantalum (Ta) and nitrogen (N) in a total content of 60 at% (atomic%, the same applies hereinafter) or more.
- the thickness of the absorber layer is preferably 5 to 100 nm.
- the low reflective layer is a layer containing tantalum (Ta), oxygen (O) and nitrogen (N) in a total content of 60 at% or more, and
- the film thickness of the low reflection layer is preferably 1 to 30 nm.
- the heat treatment is performed to form a surface oxide film on the absorber layer.
- the present invention also provides a reflective mask blank for EUVL, which is obtained by the method for producing a reflective mask blank for EUVL of the present invention and has a surface oxide film having a film thickness of 0.5 to 3 nm on the surface of the absorber layer. .
- the present invention also provides a reflective mask blank for EUVL, which is obtained by the method for producing a reflective mask blank for EUVL of the present invention and has a surface oxide film having a film thickness of 0.5 to 3 nm on the surface of the low reflective layer. .
- the term “to” indicating the above numerical range is used in the sense that the numerical values described before and after it are used as the lower limit value and the upper limit value. Unless otherwise specified, “to” is the same in the following specification. Used with meaning.
- the heat treatment is performed on the substrate on which the absorber layer is formed after the absorber layer is formed, so that the oxidation of the uppermost Si film of the Mo / Si multilayer reflective film due to the heat treatment is suppressed.
- the effect of the heat treatment that relieves the film stress by structural relaxation and mixing in the multilayer reflective film is maximized. Therefore, the effects of the heat treatment such as the relaxation of the film stress in the Mo / Si multilayer reflective film and the deformation of the substrate thereby, and the suppression of the temporal change of the film stress in the Mo / Si multilayer reflective film are improved.
- the change in the reflection characteristics of the Mo / Si multilayer reflective film is suppressed. Specifically, a decrease in the reflectance of reflected light during EUV light irradiation is suppressed.
- FIG. 1 is a schematic cross-sectional view showing an embodiment of a reflective mask blank for EUVL manufactured by the method of the present invention.
- FIG. 2 is a schematic cross-sectional view showing another embodiment of the reflective mask blank for EUVL manufactured by the method of the present invention.
- FIG. 1 is a schematic cross-sectional view showing an embodiment of a reflective mask blank for EUVL (that is, an EUV mask blank) manufactured by the method of the present invention.
- a reflective layer 12 that reflects EUV light and an absorber layer 14 that absorbs EUV light are formed on a substrate 11 in this order.
- a protective layer 13 is formed between the reflective layer 12 and the absorber layer 14 to protect the reflective layer 12 when forming a pattern on the absorber layer 14.
- the protective layer 13 is an optional component.
- individual components of the mask blank 1 will be described.
- the substrate 11 is required to satisfy the characteristics as a substrate for an EUV mask blank. Therefore, the substrate 11 preferably has a low thermal expansion coefficient of 0 ⁇ 1.0 ⁇ 10 ⁇ 7 / ° C., more preferably 0 ⁇ 0.3 ⁇ 10 ⁇ 7 / ° C., and further preferably 0 ⁇ 0.2. ⁇ 10 ⁇ 7 / ° C., more preferably 0 ⁇ 0.1 ⁇ 10 ⁇ 7 / ° C., particularly preferably 0 ⁇ 0.05 ⁇ 10 ⁇ 7 / ° C., smoothness, flatness, and mask blank or pattern Those excellent in resistance to a cleaning solution used for cleaning a photomask after formation are preferable.
- the substrate 11 is made of glass having a low thermal expansion coefficient, such as SiO 2 —TiO 2 glass, but is not limited to this. Crystallized glass, quartz glass, silicon, A substrate such as metal can also be used. A film such as a stress correction film may be formed on the substrate 11. Since the substrate 11 has a smooth surface with a surface roughness (rms) of 0.15 nm or less and a flatness of 100 nm or less, high reflectivity and transfer accuracy can be obtained in a photomask after pattern formation. Is preferred.
- the surface roughness (rms) described above is a value obtained by measuring an area of 1 ⁇ m ⁇ 1 ⁇ m with an atomic force microscope at a resolution of 1.95 nm.
- the size, thickness, etc. of the substrate 11 are appropriately determined according to the design value of the mask.
- SiO 2 —TiO 2 glass having an outer shape of 6 inches (152.4 mm) square and a thickness of 0.25 inches (6.3 mm) was used.
- the surface of the substrate 11 on the side where the reflective layer 12 is formed has no defects.
- the depth of the concave defect and the height of the convex defect are not more than 2 nm so that the phase defect does not occur due to the concave defect and / or the convex defect.
- the half width of the defect and the convex defect is 60 nm or less.
- the characteristic particularly required for the reflective layer 12 of the EUV mask blank is a high EUV light reflectance.
- the maximum value of the light reflectance near a wavelength of 13.5 nm when a light ray in the wavelength region of EUV light is irradiated onto the surface of the reflective layer 12 at an incident angle of 6 degrees is preferably 60% or more, and 63% The above is more preferable, and 65% or more is more preferable.
- the maximum value of the light reflectance near the wavelength of 13.5 nm is preferably 60% or more, more preferably 63% or more, and 65% or more. Is more preferable.
- the EUV mask blank of the present invention uses a Mo / Si multilayer reflective film in which a Mo film as a low refractive index film and a Si film as a high refractive index film are alternately laminated a plurality of times.
- Mo film and the Si film are compared, since the Si film is more stable against oxidation at room temperature in the atmosphere, the uppermost layer of the Mo / Si multilayer reflective film is oxidized on the surface of the multilayer reflective film.
- a Si film is used.
- a Mo film having a film thickness of 2.3 ⁇ 0.1 nm, and a film thickness of 4.5 ⁇ A 0.1 nm Si film may be laminated so that the number of repeating units is 30 to 60.
- a Mo / Si multilayer reflective film having the Si film as the uppermost layer is formed on the film formation surface of the substrate.
- each layer constituting the Mo / Si multilayer reflective film is well known, such as a magnetron sputtering method or an ion beam sputtering method.
- the film formation method may be used to form a film on the surface of the substrate so as to obtain a desired thickness.
- an Mo / Si multilayer reflective film is formed by ion beam sputtering
- an Mo target is used as a target
- Ar gas gas pressure 1.3 ⁇ 10 ⁇ 2 Pa to 2.7 ⁇ 10 ⁇
- a sputtering gas is used as a sputtering gas. 2 Pa
- an Mo film is formed to have a thickness of 2.3 nm at an ion acceleration voltage of 300 to 1500 V and a film formation rate of 1.8 to 18.0 nm / min.
- the Si film is formed by laminating the Mo film and the Si film for 30 to 60 cycles.
- the protective layer 13 is an arbitrary configuration provided for the purpose of protecting the reflective layer 12 so that the reflective layer 12 is not damaged by the etching process when the absorber layer 14 is patterned by an etching process, usually a dry etching process. Is an element. However, from the viewpoint of protecting the reflective layer 12, it is preferable to form the protective layer 13 on the reflective layer 12.
- the protective layer 13 As the material of the protective layer 13, a material that is not easily affected by the etching process of the absorber layer 14, that is, the etching rate is slower than that of the absorber layer 14 and is not easily damaged by the etching process.
- the protective layer 13 itself selects a substance having a high EUV light reflectivity so that the EUV light reflectivity in the reflective layer 12 is not impaired even after the protective layer 13 is formed. It is preferable.
- the Ru content in the protective layer 13 is preferably 50 at% or more, more preferably 70 at% or more, further preferably 90 at% or more, and particularly 95 at%. % Or more is preferable.
- the surface roughness (rms) of the surface of the protective layer 13 is preferably 0.5 nm or less. If the surface roughness of the surface of the protective layer 13 is large, the surface roughness of the absorber layer 14 formed on the protective layer 13 increases, and the edge roughness of the pattern formed on the absorber layer 14 increases. The dimensional accuracy of the pattern deteriorates. Since the influence of edge roughness becomes more prominent as the pattern becomes finer, the surface of the absorber layer 14 is required to be smooth. If the surface roughness (rms) of the surface of the protective layer 13 is 0.5 nm or less, the surface of the absorber layer 14 formed on the protective layer 13 is sufficiently smooth.
- the surface roughness (rms) of the surface of the protective layer 13 is more preferably 0.4 nm or less, and further preferably 0.3 nm or less.
- the thickness of the protective layer 13 is preferably 1 to 10 nm because the EUV light reflectance can be increased and the etching resistance can be obtained.
- the thickness of the protective layer 13 is more preferably 1 to 5 nm, and further preferably 2 to 4 nm.
- the protective layer 13 can be formed using a known film forming method such as a magnetron sputtering method or an ion beam sputtering method.
- a Ru layer is formed as the protective layer 13 using an ion beam sputtering method
- a Ru target may be used as a target and discharged in an argon (Ar) atmosphere.
- ion beam sputtering may be performed under the following conditions.
- Ion acceleration voltage 300-1500V
- Deposition rate 1.8 to 18.0 nm / min.
- the characteristic particularly required for the absorber layer 14 is that the EUV light reflectance is extremely low. Specifically, the maximum light reflectance around a wavelength of 13.5 nm when the surface of the absorber layer 14 is irradiated with light in the wavelength region of EUV light is preferably 2.0% or less, and 1.0% or less. More preferred. In order to achieve the above characteristics, a configuration with a material having a high EUV light absorption coefficient is preferable, and it is preferable to be formed with a material mainly composed of tantalum (Ta). Furthermore, in the EUV mask blank of the present invention, the Si film that forms the uppermost layer of the Mo / Si multilayer reflective film is oxidized on the absorber layer 14 during the heat treatment performed after the formation of the absorber layer 14.
- the absorber layer 14 preferably has no crystal grain boundaries, that is, has an amorphous crystal state, in order to prevent oxygen diffusion, and Ta and nitrogen.
- the TaN layer containing (N) is preferable in that it easily forms a film having an amorphous crystal state.
- the total content of Ta and N is preferably 60 at% or more in order to exhibit the function as the barrier layer described above, more preferably 80 at% or more. More preferably 95 at% or more.
- the content and composition ratio of Ta and N preferably satisfy the following ranges.
- Ta content is preferably 10 to 95 at%, more preferably 60 to 90 at%, N content preferably 5 to 50 at%, more preferably 10 to 40 at%, Composition ratio of Ta and N (Ta: N) 8: 1 to 1: 5.
- the edge roughness of the pattern formed on the absorber layer 14 increases and the dimensional accuracy of the pattern deteriorates. Since the influence of edge roughness becomes more prominent as the pattern becomes finer, the surface of the absorber layer 14 is required to be smooth.
- the crystal state is amorphous and the surface smoothness is excellent.
- the surface roughness (rms) of the surface of the absorber layer 14 is 0.5 nm or less.
- the surface roughness (rms) of the surface of the absorber layer 14 is 0.5 nm or less, the surface of the absorber layer 14 is sufficiently smooth, and there is no possibility that the dimensional accuracy of the pattern is deteriorated due to the influence of edge roughness.
- the surface roughness (rms) of the surface of the absorber layer 14 is more preferably 0.4 nm or less, and further preferably 0.3 nm or less.
- the etching rate is high when dry etching is performed using a chlorine-based gas as an etching gas, and the protective layer 13 (specifically, a Ru layer or a Ru compound layer)
- the etching selectivity ratio is 10 or more.
- the etching selection ratio with the reflective layer 12 is 10 or more.
- the etching selectivity is preferably 10 or more, more preferably 11 or more, and still more preferably 12 or more.
- the thickness of the absorber layer 14 is preferably 5 nm or more, more preferably 20 nm or more, further preferably 30 nm or more, and particularly preferably 50 nm or more.
- the thickness is preferably 100 nm or less, more preferably 90 nm or less, and even more preferably 80 nm or less.
- the absorber layer 14 can be formed using a known film forming method such as a magnetron sputtering method or a sputtering method such as an ion beam sputtering method.
- a TaN layer is formed as the absorber layer 14 and a magnetron sputtering method is used, a Ta target is used, and the target is discharged in a nitrogen (N 2 ) atmosphere diluted with Ar to form the TaN layer. it can.
- Sputtering gas Mixed gas of Ar and N 2 (N 2 gas concentration is 3 to 80 vol%, preferably 5 to 30 vol%, more preferably 8 to 15 vol%.
- Gas pressure is 0.5 ⁇ 10 ⁇ 1 Pa ⁇ 10 ⁇ 10 ⁇ 1 Pa, preferably 0.5 ⁇ 10 ⁇ 1 Pa to 5 ⁇ 10 ⁇ 1 Pa, more preferably 0.5 ⁇ 10 ⁇ 1 Pa to 3 ⁇ 10 ⁇ 1 Pa.
- the substrate on which the absorber layer is formed is heat-treated at a temperature of 110 to 170 ° C., preferably 120 to 160 ° C.
- This heat treatment promotes structural relaxation of each layer constituting the Mo / Si multilayer reflective film and mixing of the interface.
- the film stress (that is, compressive stress) of the Mo / Si multilayer reflective film is relieved by the contraction of the Mo / Si multilayer reflective film due to the promotion of structural relaxation and mixing. That is, the effect of heat treatment is exerted to relieve the film stress by the structure relaxation and mixing in the Mo / Si multilayer reflective film.
- substrate is relieve
- the structural relaxation and the promotion of mixing suppress the change with time in the stress of the Mo / Si multilayer reflective film.
- the absorber layer functions as a barrier layer, the oxidation of the Si film that forms the uppermost layer of the Mo / Si multilayer reflective film due to the heat treatment is suppressed. Thereby, an increase in film stress due to oxidation of the Si film is suppressed. As a result, the effect of the heat treatment that relieves the film stress by the structural relaxation and mixing in the multilayer reflective film is maximized. Further, by suppressing the oxidation of the uppermost Si film of the Mo / Si multilayer reflective film, the change in the reflection characteristics of the Mo / Si multilayer reflective film is suppressed. Specifically, a decrease in the reflectance of reflected light during EUV light irradiation is suppressed.
- a protective layer may be formed on the Mo / Si multilayer reflective film.
- these protective layers are removed from the Mo / Si multilayer reflective film by an etching process.
- a constituent material for example, Ru or Ru compound
- the protective layer is preferably small in thickness, specifically, the thickness is preferably 1 to 10 nm.
- the film stress that is, compressive stress
- the oxidation of these films may change their optical constants, which may change the reflection characteristics during EUV light irradiation. Specifically, the reflectance of reflected light during EUV light irradiation may be reduced.
- the absorber layer functions as a barrier layer
- the uppermost Si film of the Mo / Si multilayer reflective film due to oxidation of the Ru film or Ru compound film as the protective layer or oxygen diffused from the surface of the protective layer Is also suppressed. Also by these actions, the effect of relaxing the film stress of the multilayer reflective film and the effect of suppressing the change in the reflection characteristics of the multilayer reflective film are exhibited.
- the specific temperature of the heat treatment may be adjusted in a range of 110 to 170 ° C., preferably 120 to 160 ° C., so that a desired stress relaxation amount is obtained.
- the heat treatment temperature is lower than 110 ° C., the effect of the heat treatment that relaxes the film stress by structural relaxation and mixing in the Mo / Si multilayer reflective film becomes insufficient.
- the heat treatment temperature is higher than 170 ° C., the mixing in the Mo / Si multilayer reflective film proceeds too much, and each layer of the multilayer reflective film contracts greatly, changing the reflection characteristics when irradiated with EUV light. In some cases, the reflectance of reflected light during EUV light irradiation may decrease.
- the temperature of the heat treatment is more preferably 130 ° C. to 150 ° C., further preferably 136 ° C. to 144 ° C.
- the heating time is preferably in the range of 5 to 60 minutes, more preferably in the range of 10 to 30 minutes.
- the heat treatment time is shorter than 5 minutes, there is a possibility that the effect of the heat treatment, which relaxes the film stress by structural relaxation and mixing in the Mo / Si multilayer reflective film, may be insufficient.
- the heat treatment time is longer than 60 minutes, mixing proceeds too much and each layer of the multilayer reflective film contracts greatly, and changes in reflection characteristics during EUV light irradiation, specifically, reflection during EUV light irradiation. There is a possibility that the reflectance of light may decrease.
- the heat treatment in the present invention can be carried out in a vacuum or in an air atmosphere.
- the generation of defects from the vacuum chamber wall and the adhesion to the EUV mask blank due to the heat history generated by the heat treatment in vacuum can be suppressed, and the atmosphere such as nitrogen gas under atmospheric pressure. It is preferable because it can be easily handled without taking safety measures against suffocation when handling other gases.
- a surface oxide film having a certain thickness or more is formed on the surface of the absorber layer, and the absorber layer is subjected to changes in optical properties and compression stress due to the oxidation. Since the effect which protects from an increase is acquired, it is preferable.
- a TaON layer is formed on the surface of the absorber layer by heat treatment in the air atmosphere, and this functions as a film that protects TaN under the surface oxide film from further oxidation.
- the surface oxide film formed by the method of the present invention preferably has a thickness of 0.5 to 3 nm, more preferably 1.5 to 2.5 nm. If the thickness is less than 0.5 nm, the surface of the absorber layer is not sufficiently protected and the durability against washing may be reduced. For example, even when the absorber layer is formed and left at room temperature in the atmosphere without heat treatment, an extremely thin surface oxide film is formed, but the film thickness is at most 0.2 nm. The durability of the layer cannot be improved.
- the method for forming a surface oxide film having a constant thickness on the surface of the absorber layer as described above is not limited to heat treatment in an air atmosphere.
- an oxygen (O 2 ) and nitrogen (N 2 ) atmosphere diluted with an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe) Heat treatment may be performed in the inside, or heat treatment may be performed in an atmosphere exposed to oxygen plasma.
- the film thickness is preferably 0.5 to 3 nm, more preferably 1.5 to 2.5 nm.
- FIG. 2 is a schematic cross-sectional view showing another embodiment of the EUV mask blank of the present invention.
- a low reflection layer 15 for inspection light used for inspection of a mask pattern is formed on the absorber layer 14.
- the protective layer 13 is formed on the reflective layer 12 as an aspect of the EUV mask blank, the former surface (that is, the surface exposed by removing the absorber layer 14 by pattern formation) is the protective layer 13.
- the former surface is the surface of the reflective layer 12 (specifically, the uppermost layer of the Mo / Si multilayer reflective film). Si film surface). Therefore, if the difference in reflectance between the surface of the protective layer 13 (or the surface of the reflective layer 12) and the surface of the absorber layer 14 with respect to the wavelength of the inspection light of about 257 nm is too small, the contrast at the time of inspection deteriorates and accurate inspection cannot be performed. There is a case.
- the inspection light is referred to in this specification, the light having a wavelength of 257 nm is indicated unless the wavelength is particularly described.
- the absorber layer 14 having the above-described configuration has an extremely low EUV light reflectance, and has excellent characteristics as an absorber layer of an EUV mask blank.
- the light reflectance is not necessarily limited. It's not low enough.
- the difference between the reflectance of the surface of the absorber layer 14 at the wavelength of the inspection light and the reflectance of the surface of the reflective layer 12 (or the surface of the protective layer 13) becomes small, and there is a possibility that sufficient contrast at the time of inspection cannot be obtained. is there. If sufficient contrast at the time of inspection is not obtained, pattern defects may not be sufficiently determined in mask inspection, and accurate defect inspection may not be performed.
- the low reflection layer 15 is formed on the absorber layer 14, so that the contrast at the time of inspection becomes good.
- the light reflectance at the wavelength of the inspection light is extremely low.
- the maximum light reflectance of the wavelength of the inspection light when irradiated with light in the wavelength region (near 257 nm) of the inspection light is preferably 15% or less, and 10% The following is more preferable, and 5% or less is more preferable. If the light reflectance at the wavelength of the inspection light in the low reflection layer 15 is 15% or less, the contrast at the time of the inspection is good. Specifically, the contrast between the reflected light having the wavelength of the inspection light on the surface of the protective layer 13 (or the surface of the reflective layer 12) and the reflected light having the wavelength of the inspection light on the surface of the low reflective layer 15 is 40% or more. .
- Contrast (%) ((R 2 ⁇ R 1 ) / (R 2 + R 1 )) ⁇ 100
- R 2 at the wavelength of the inspection light is the reflectance at the surface of the protective layer 13 (or the surface of the reflective layer 12)
- R 1 is the reflectance at the surface of the low reflective layer 15.
- R 1 and R 2 are measured in a state where patterns are formed on the absorber layer 14 and the low reflection layer 15 of the EUV mask blank 1 ′ shown in FIG.
- R 2 is a value measured on the surface of the protective layer 13 (or the surface of the reflective layer 12) exposed to the outside after the absorber layer 14 and the low reflective layer 15 are removed by pattern formation, and R 1 is removed by pattern formation. It is a value measured on the surface of the low reflection layer 15 remaining without being removed.
- the contrast represented by the above formula is more preferably 45% or more, further preferably 60% or more, and particularly preferably 70% or more.
- the low reflective layer 15 is made of a material whose refractive index at the wavelength of the inspection light is lower than that of the absorber layer 14, and its crystalline state is preferably amorphous.
- a specific example of such a low reflection layer 15 is a TaON layer containing Ta, oxygen (O) and nitrogen (N) in the ratios described below.
- the total content of Ta, O and N is preferably 60 at% or more, more preferably 80 at% or more, and further preferably 95 at% or more.
- the content and composition ratio of Ta, O, and N preferably satisfy the following ranges.
- Ta content 20 to 80 at%, preferably 20 to 70 at%, more preferably 20 to 60 at%, Total content of O and N: 20 to 80 at%, preferably 30 to 80 at%, more preferably 40 to 80 at%, Composition of O and N (O: N): 20: 1 to 1:20, preferably 18: 1 to 1:18, more preferably 15: 1 to 1:15.
- the crystalline state is amorphous due to its configuration, and the surface thereof is excellent in smoothness.
- the surface roughness (rms) of the surface of the low reflection layer 15 is 0.5 nm or less.
- the surface of the absorber layer 14 is required to be smooth in order to prevent deterioration of the dimensional accuracy of the pattern due to the influence of edge roughness. Since the low reflection layer 15 is formed on the absorber layer 14, the surface thereof is required to be smooth for the same reason.
- the surface roughness (rms) of the surface of the low reflection layer 15 is 0.5 nm or less, the surface of the low reflection layer 15 is sufficiently smooth, and there is no possibility that the dimensional accuracy of the pattern is deteriorated due to the influence of edge roughness.
- the surface roughness (rms) of the surface of the low reflective layer 15 is more preferably 0.4 nm or less, and further preferably 0.3 nm or less.
- the total thickness of the absorber layer 14 and the low reflection layer 15 is preferably 20 to 130 nm. Further, if the thickness of the low reflection layer 15 is larger than the thickness of the absorber layer 14, the EUV light absorption characteristics in the absorber layer 14 may be deteriorated. Therefore, the thickness of the low reflection layer 15 is determined by the absorber layer. It is preferred that the thickness be less than 14. For this reason, the thickness of the low reflection layer 15 is preferably 1 to 30 nm, more preferably 5 to 30 nm, and even more preferably 10 to 20 nm.
- the low reflection layer (TaON) having the above-described configuration is formed by oxygen diluted with an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe)
- an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe) It can be formed by sputtering using a Ta target, for example, magnetron sputtering or ion beam sputtering, in an O 2 ) and nitrogen (N 2 ) atmosphere.
- the Ta target is discharged in a nitrogen (N 2 ) atmosphere diluted with an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe).
- the low reflection of the above structure is obtained by oxidizing the formed film by, for example, exposing it to oxygen plasma or irradiating an ion beam using oxygen. It is good also as a layer (TaON).
- Sputtering gas Ar, O 2 and N 2 mixed gas (O 2 gas concentration 5 to 80 vol%, N 2 gas concentration 5 to 75 vol%, preferably O 2 gas concentration 6 to 70 vol%, N 2 gas concentration 6 to 35 vol) %, More preferably O 2 gas concentration 10-30 vol%, N 2 gas concentration 10-30 vol%, Ar gas concentration 5-90 vol%, preferably 10-88 vol%, more preferably 20-80 vol%, Gas pressure of sputtering gas: 1.0 ⁇ 10 ⁇ 1 Pa to 50 ⁇ 10 ⁇ 1 Pa, preferably 1.0 ⁇ 10 ⁇ 1 Pa to 40 ⁇ 10 ⁇ 1 Pa, more preferably 1.0 ⁇ 10 ⁇ 1 Pa to 30 ⁇ 10 ⁇ 1 Pa, Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W, Deposition rate: 0.1 to 50 nm / min, preferably 0.2 to 45
- concentration of the inert gas sets it as the same concentration range as above-mentioned Ar gas concentration.
- the total concentration of the inert gases is in the same concentration range as the Ar gas concentration described above.
- the above-described heat treatment is performed after the low reflective layer 15 is formed.
- the atmosphere is the same as the heat treatment after the formation of the absorber layer 14 in the mask blank 1 shown in FIG. That is, a surface oxide film may be formed on the surface of the low reflective layer 15 by a heat treatment method under desired conditions in an air atmosphere or in a vacuum.
- the heat treatment temperature after the formation of the low reflection layer 15 on the substrate on which the low reflection layer 15 is formed is also the same temperature as the heat treatment after the formation of the absorber layer 14, that is, a range of 110 to 170 ° C.
- the temperature of the heat treatment is 120 to 160 ° C., further preferably 130 to 150 ° C., and further preferably 136 to 144 ° C.
- the heating time is preferably in the range of 5 to 60 minutes, more preferably in the range of 10 to 30 minutes.
- the thickness of the surface oxide film formed on the surface of the low reflective layer 15 is preferably 0.5 to 3 nm, and more preferably 1.5 to 2.5 nm. If the thickness is less than 0.5 nm, the surface of the absorber layer is not sufficiently protected, and the durability against cleaning may be reduced. On the other hand, if the thickness is greater than 3 nm, the maximum light reflectance for the inspection light of the mask pattern increases, and the contrast may be reduced.
- the surface oxide film formed by the heat treatment after the low reflective layer is formed is oxygen-rich TaON, that is, TaON configured as a low reflective layer.
- the composition has a large composition of oxygen (O), and can be recognized as a layer having a composition different from that of the low reflection layer TaON in this case.
- the surface oxide film on TaON can be identified by the composition of oxygen, and a layer having a composition ratio of oxygen of 5 at% or more with respect to the TaON layer serving as a low reflection layer is used as the surface oxide film. Can be identified.
- the reason why the low reflection layer 15 is preferably formed on the absorber layer 14 as in the EUV mask blank 1 ′ shown in FIG. 2 is that the pattern inspection light wavelength and the EUV light wavelength are different. Therefore, when EUV light (around 13.5 nm) is used as the pattern inspection light, it is considered unnecessary to form the low reflection layer 15 on the absorber layer 14.
- the wavelength of the inspection light tends to shift to the short wavelength side as the pattern size becomes smaller, and it is conceivable that it will shift to 193 nm and further to 13.5 nm in the future.
- the wavelength of the inspection light is 193 nm, it may not be necessary to form the low reflection layer 15 on the absorber layer 14. Further, when the wavelength of the inspection light is 13.5 nm, it is considered unnecessary to form the low reflection layer 15 on the absorber layer 14.
- the EUV mask blank of the present invention may have a functional film known in the field of EUV mask blanks.
- a functional film for example, as described in Japanese Patent Publication No. 2003-501823, a high dielectric coating applied to the back side of the substrate in order to promote electrostatic chucking of the substrate Is mentioned.
- the back surface of the substrate refers to a surface of the substrate 11 in FIG. 1 opposite to the film forming surface on which the reflective layer 12 is formed.
- the electrical conductivity and thickness of the constituent material are selected so that the sheet resistance is 100 ⁇ / ⁇ or less.
- the constituent material of the high dielectric coating can be widely selected from those described in known literature.
- a high dielectric constant coating described in Japanese Patent Special Publication No. 2003-501823 specifically, a coating made of silicon, TiN, molybdenum, chromium, and TaSi can be applied.
- the thickness of the high dielectric coating is, for example, 10 to 1000 nm.
- the high dielectric coating can be formed using a known film forming method, for example, a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, a CVD method, a vacuum evaporation method, or an electrolytic plating method.
- Example 1 the EUV mask blank 1 shown in FIG. 1 was produced.
- a SiO 2 —TiO 2 glass substrate (outer dimensions 6 inches (152.4 mm) square, thickness 6.3 mm) was used.
- This glass substrate has a thermal expansion coefficient of 0.2 ⁇ 10 ⁇ 7 / ° C., a Young's modulus of 67 GPa, a Poisson's ratio of 0.17, and a specific rigidity of 3.07 ⁇ 10 7 m 2 / s 2 .
- This glass substrate was polished to form a smooth surface with a surface roughness (rms) of 0.15 nm or less and a flatness of 100 nm or less.
- a high dielectric coating (not shown) having a sheet resistance of 100 ⁇ / ⁇ was applied to the back surface of the substrate 11 by depositing a Cr film having a thickness of 100 nm using a magnetron sputtering method.
- a substrate 11 (outer dimensions 6 inches (152.4 mm) square, thickness 6.3 mm) is fixed to a normal electrostatic chuck having a flat plate shape using the Cr film formed by the above-described procedure.
- Mo / Si multilayer having a total film thickness of 340 nm ((2.3 nm + 4.5 nm) ⁇ 50) is obtained by repeating 50 cycles of alternately forming a Mo film and a Si film on the surface of the substrate by ion beam sputtering.
- a reflective film (reflective layer 12) was formed.
- the uppermost layer of the Mo / Si multilayer reflective film is a Si film.
- the film forming conditions for the Mo film and the Si film are as follows.
- Target Mo target
- Sputtering gas Ar gas (gas pressure 0.02 Pa)
- Film thickness 2.3 nm.
- Si film formation conditions Target: Si target (boron-doped Si target), Sputtering gas: Ar gas (gas pressure 0.02 Pa), Voltage: 700V Deposition rate: 4.62 nm / min, Film thickness: 4.5 nm.
- a Ru layer as the protective layer 13 was formed by using an ion beam sputtering method.
- the formation conditions of the protective layer 13 are as follows.
- TaN layer deposition conditions Target: Ta target, Sputtering gas: mixed gas of Ar and N 2 (Ar: 86vol%, N 2: 14vol%, gas pressure: 0.3 Pa), Input power: 150W Deposition rate: 7.2 nm / min, Film thickness: 60 nm.
- the EUV mask blank after the formation of the absorber layer 14 was heat-treated for 20 minutes while being controlled within the range of 140 ⁇ 4 ° C. in an air atmosphere.
- the heating temperature is the temperature of the mask blank surface
- the heating time is the time during which the temperature of the mask blank surface is maintained within the range of 140 ⁇ 4 ° C.
- a surface oxide film formed by heat treatment of the absorber layer 14 on the surface of the TaN layer to be the absorber layer 14, that is, a TaON surface oxide film is a highly functional thin film X-ray reflectivity film manufactured by Rigaku. When the film thickness was measured by the X-ray reflectivity measurement method using a thickness measuring apparatus, it was 2 nm.
- the surface of the EUV mask blank refers to the surface of the absorber layer 14.
- the back surface of the EUV mask blank refers to the surface of the Cr film formed on the back surface side of the substrate 11.
- Example 2 an EUV mask blank 1 ′ shown in FIG. 2 was produced.
- the substrate 11 is the same as that in Example 1, and further, a Cr layer serving as a high dielectric coating on the back side of the substrate 11, a Mo / Si multilayer reflective film (reflective layer 12). ),
- the Ru layer to be the protective layer 13 and the TaN layer to be the absorber layer 14 were formed under the same conditions as in Example 1.
- TaON layer deposition conditions Target: Ta target, Sputtering gas: Ar, O 2 and N 2 mixed gas (Ar: 49 vol%, O 2 : 37 vol%, N 2 : 14 vol%, gas pressure: 0.3 Pa), Input power: 250W Deposition rate: 2.0 nm / min, Film thickness: 8 nm.
- the EUV mask blank after the formation of the low reflection layer 15 was controlled to be within a range of 140 ⁇ 4 ° C. for 20 minutes in an air atmosphere.
- the heating temperature is the temperature of the mask blank surface
- the heating time is the time during which the temperature of the mask blank surface is maintained within the range of 140 ⁇ 4 ° C.
- a surface oxide film formed by heat treatment of the low reflection layer 15 on the surface of the TaON layer to be the low reflection layer 15 is measured using a high-performance thin film X-ray reflectivity film thickness measuring device manufactured by Rigaku.
- the film thickness is measured by the linear reflectance measurement method, it is about 2 nm.
- Comparative Example 1 After forming up to the protective layer 13 in the same procedure as in Example 1, the EUV mask blank after the formation of the protective layer 13 is controlled to be within a range of 140 ⁇ 4 ° C. in an air atmosphere and heat-treated for 20 minutes.
- the absorber layer 14 was formed after the treatment. That is, in Comparative Example 1, the heat treatment was performed in the state before the absorber layer 14 was formed. Regarding the measurement of the flatness before and after the heat treatment, the flatness measurement before the heat treatment was performed after the formation of the protective layer 13, and the flatness measurement after the heat treatment was performed after the absorber layer 14 was formed.
- Example 1 The difference in flatness between before and after the heat treatment indicates how much the warpage of the substrate 11 caused by the film stress is alleviated by the heat treatment. As is apparent from the both, the effect of alleviating the warpage of the substrate was improved by performing the heat treatment after the absorber layer was formed.
- the relaxation of the film stress in the Mo / Si multilayer reflective film of the EUV mask blank, the relaxation of the substrate deformation caused thereby, and the temporal change of the film stress in the Mo / Si multilayer reflective film are suppressed.
- the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2011-257749 filed on November 25, 2011 are incorporated herein as the disclosure of the present invention. .
- EUV mask blank 11 Substrate 12: Reflective layer (Mo / Si multilayer reflective film) 13: Protective layer 14: Absorber layer 15: Low reflective layer
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Abstract
Description
吸収体層には、EUV光に対する吸収係数の高い材料、具体的にはたとえば、クロム(Cr)やタンタル(Ta)を主成分とする材料が用いられる。
このような高い膜応力が基板に加わることによって、基板が変形するおそれがある。EUVマスクブランク用の基板には通常低膨張ガラス製の基板が使用されるので、膜応力が加わることによって生じる基板の変形は軽微であるため、従来問題とならなかった。
しかしながら、パターンの微細化の要請によって、従来問題視されなかった基板の微少な変形(即ち、膜応力が加わることによって生じる基板の変形)が問題となってきた。たとえば、EUVマスクブランクの基板に特定の大きさ以上の変形が存在する場合、具体的には、EUVマスクブランクの製造に通常使用される152mm角の基板の場合、基板の反り量が0.6μmを超えると、該EUVマスクブランクをパターニングする際にパターンの位置精度が低下するおそれがある。また、このような大きさの反りが発生すると、該EUVマスクブランクから作製した反射型マスクを用いてパターン転写する際に、パターン位置ずれやパターン欠陥が発生するおそれがある。
特許文献1には、このような膜応力の変化は、多層反射膜を構成している各層界面の極僅かなミキシングに起因していると記載されている。この変化は、X線反射率膜厚測定による周期長測定では検出できないレベルであるが、これにより、多層反射膜の反射率のピーク波長(即ち、多層反射膜の反射率のピークが最大である波長)は、0.01nmのレベルで変化をする。EUV光は非常に短波長の光なので、多層反射膜の状態の変化が、非常に敏感にその波長特性、反射特性に影響を及ぼすとされている。
又、EUVリソグラフィでは、特定の狭い波長帯域の光を使用するため、波長シフトの影響は大きく、反射率のピーク波長のシフトは、パターン転写時に使用する露光機のミラーとのミスマッチを起こしてしまうため、ピーク波長は正確に制御されていなければならない。更には、ピーク波長のシフトによって、多層反射膜の反射率が低下してしまう。このように、多層反射膜の応力の経時変化は、基板の平坦度の変化を生じるなど、マスクの実用的な使用において色々問題になる。
特許文献1では、加熱処理の前後に多層反射膜のピーク波長と反射率を測定して、各々のピーク波長と反射率の差によるピーク波長の変化と反射率の低下が、パターン転写装置の反射ミラーとのマッチングにずれが生じることによる半導体基板上に形成するパターンサイズが実質的に変動しないものであるかを検査するため、吸収体層を形成する前に加熱処理を実施することが好ましいとしている。
また、特許文献1では、基板上に形成した多層反射膜を加熱保持された液体と接触させることにより上記の加熱処理を実施している。さらには、特許文献1では、加熱処理に用いる液体として、洗浄液を使用することで、加熱処理と洗浄工程を同時に行うことができるとしている。
このため、本発明者らは、特許文献1に記載の加熱処理による多層反射膜への影響について鋭意検討した。その結果、多層反射膜を構成する各層の構造緩和と界面のミキシングの進行により、多層反射膜を構成する各層が収縮して膜応力が緩和されること、および、膜応力の緩和により基板の変形が緩和されることを確認した。以下、本明細書において、多層反射膜を構成する各層の構造緩和と界面のミキシングの進行により、多層反射膜を構成する各層が収縮して膜応力が緩和されることを、多層反射膜での構造緩和とミキシングによる膜応力の緩和という場合がある。
しかしながら、加熱処理により多層反射膜での構造緩和とミキシングにより膜応力が緩和される一方で、加熱処理の条件によっては、所望の値を満たさない程度に、EUV光照射時の反射特性の変化も併せて引き起こされる場合がある。具体的には、多層反射膜でのミキシングが進行しすぎると、多層反射膜の各層が層の厚さ方向に大きく収縮し、EUV光照射時の反射特性、すなわち、反射光のピーク波長と反射率が低下するおそれがある。
また、加熱処理時に多層反射膜の表面が酸化されることによって、上述した加熱処理による効果、すなわち、多層反射膜での構造緩和とミキシングによる膜応力の緩和が阻害されることが明らかになった。
加熱処理の実施時、大気に面したMo/Si多層反射膜の最上層のSi膜表面へ、大気の酸素が吸着、拡散し、この酸素が、該Si膜中のSi原子と結合し、Si膜の構造が膨張することにより、該Si膜での膜応力(圧縮応力)が増加する。
これにより、上述した加熱処理による効果、すなわち、多層反射膜での構造緩和とミキシングによる膜応力の緩和が阻害される。
Mo/Si多層反射膜上に保護層として、Ru膜やRu化合物(RuB等)膜が形成された多層反射膜付き基板に対し加熱処理を実施した場合においても、大気に面した膜(即ち、Ru膜やRu化合物膜)表面から拡散した酸素によって、Mo/Si多層反射膜の最上層のSi膜が酸化されることによって、該Si膜での膜応力(圧縮応力)が増加する。
また、一般的にSi膜以外の膜が酸化された場合も膜応力(圧縮応力)が増加する。したがって、保護層としてのRu膜やRu化合物膜が酸化されることでも、膜応力(圧縮応力)が増加する。
Mo/Si多層反射膜上に、保護層としてRu膜やRu化合物膜が形成されている場合にも、Ru膜やRu化合物膜の酸化によっても、それらの光学定数が変化して、EUV光照射時の反射特性が変化するおそれがある。具体的には、反射光の反射率が低下するおそれもある。
前記多層反射膜が、Mo/Si多層反射膜であり、かつ、該Mo/Si多層反射膜の最上層がSi膜であり、
前記吸収体層の形成後、該吸収体層が形成された基板を110~170℃、好ましくは120~160℃の温度で加熱処理するEUVL用反射型マスクブランクの製造方法を提供する。
前記多層反射膜が、Mo/Si多層反射膜であり、かつ、該Mo/Si多層反射膜の最上層がSi膜であり、
前記低反射層の形成後、該低反射層が形成された基板を110~170℃、好ましくは120~160℃の温度で加熱処理するEUVL用反射型マスクブランクの製造方法を提供する。
本発明のEUVL用反射型マスクブランクの製造方法において、前記多層反射膜の形成後、前記多層反射膜上に該多層反射膜の保護層を形成し、該保護層上に前記吸収体層を形成し、該吸収体層上に前記低反射層を形成し、該低反射層の形成後、該低反射層が形成された基板に対し前記した加熱処理を施すことが好ましい。
前記保護層は、Ru層、または、Ru化合物層であることが好ましい。
本発明のEUVL用反射型マスクブランクの製造方法において、前記低反射層が、タンタル(Ta)、酸素(O)および窒素(N)を合計含有率で60at%以上含有する層であり、かつ、前記低反射層の膜厚が1~30nmであることが好ましい。
前記吸収体層上に低反射層を形成する場合は、前記加熱処理を実施して、前記低反射層上に表面酸化膜を形成することが好ましい。
また、本発明は、本発明のEUVL用反射型マスクブランクの製造方法によって得られる、前記低反射層表面に膜厚0.5~3nmの表面酸化膜を有するEUVL用反射型マスクブランクを提供する。
上記した数値範囲を示す「~」とは、その前後に記載された数値を下限値および上限値として含む意味で使用され、特段の定めがない限り、以下本明細書において「~」は、同様の意味をもって使用される。
また、該Si膜の酸化の抑制により、Mo/Si多層反射膜の反射特性の変化が抑制される。具体的には、EUV光照射時における反射光の反射率の低下が抑制される。
図1は、本発明の方法により製造されるEUVL用反射型マスクブランク(即ち、EUVマスクブランク)の1実施形態を示す概略断面図である。図1に示すEUVマスクブランク1は、基板11上にEUV光を反射する反射層12と、EUV光を吸収する吸収体層14とがこの順に形成されている。反射層12と吸収体層14との間には、吸収体層14へのパターン形成時に反射層12を保護するための保護層13が形成されている。
なお、本発明のEUVマスクブランクにおいて、図1に示す構成中、基板11、反射層12、および、吸収体層14のみが必須であり、保護層13は任意の構成要素である。
以下、マスクブランク1の個々の構成要素について説明する。
そのため、基板11は、低熱膨張係数が0±1.0×10-7/℃であることが好ましく、より好ましくは0±0.3×10-7/℃、さらに好ましくは0±0.2×10-7/℃、さらに好ましくは0±0.1×10-7/℃、特に好ましくは0±0.05×10-7/℃であり、平滑性、平坦度、およびマスクブランクまたはパターン形成後のフォトマスクの洗浄等に用いる洗浄液への耐性に優れたものが好ましい。基板11としては、具体的には低熱膨張係数を有するガラス、例えばSiO2-TiO2系ガラス等を用いるが、これに限定されず、β石英固溶体を析出した結晶化ガラスや石英ガラスやシリコンや金属などの基板も使用できる。また、基板11上に応力補正膜のような膜を形成してもよい。
基板11は、表面粗さ(rms)が0.15nm以下の平滑な表面と、100nm以下の平坦度を有していることがパターン形成後のフォトマスクにおいて高反射率および転写精度が得られるために好ましい。
上記した表面粗さ(rms)は、原子間力顕微鏡で1μm×1μmのエリアを解像度1.95nmにて測定して求めた値である。
基板11の大きさや厚さなどは、マスクの設計値等により適宜決定される。後で示す実施例では、外形6インチ(152.4mm)角で、厚さ0.25インチ(6.3mm)のSiO2-TiO2系ガラスを用いた。
基板11の反射層12が形成される側の表面には欠点が存在しないことが好ましい。しかし、存在している場合であっても、凹状欠点および/または凸状欠点によって位相欠点が生じないように、凹状欠点の深さおよび凸状欠点の高さが2nm以下であり、かつこれら凹状欠点および凸状欠点の半値幅が60nm以下であることが好ましい。
Mo/Si多層反射膜の場合に、EUV光線反射率の最大値が60%以上の反射層12とするには、膜厚2.3±0.1nmのMo膜と、膜厚4.5±0.1nmのSi膜とを繰り返し単位数が30~60になるように積層させればよい。
また、保護層13は、保護層13を形成した後であっても反射層12でのEUV光線反射率を損なうことがないように、保護層13自体もEUV光線反射率が高い物質を選択することが好ましい。
本発明のEUVマスクブランクでは、上記の条件を満足するため、保護層13として、Ru層、または、Ru化合物(例えば、RuB等)層を形成することが好ましい。保護層13として、Ru層、または、Ru化合物を形成する場合、保護層13中のRuの含有率は、50at%以上が好ましく、70at%以上がより好ましく、90at%以上がさらに好ましく、特に95at%以上が好ましい。
保護層13表面の表面粗さ(rms)が0.5nm以下であれば、該保護層13上に形成される吸収体層14表面が十分平滑であるため、エッジラフネスの影響によってパターンの寸法精度が悪化するおそれがない。保護層13表面の表面粗さ(rms)は、0.4nm以下がより好ましく、0.3nm以下がさらに好ましい。
イオンビームスパッタリング法を用いて、保護層13としてRu層を形成する場合、ターゲットとしてRuターゲットを用い、アルゴン(Ar)雰囲気中で放電させればよい。具体的には、以下の条件でイオンビームスパッタリングを実施すればよい。
スパッタリングガス:Ar(ガス圧1.3×10-2Pa~2.7×10-2Pa)、
イオン加速電圧:300~1500V、
成膜速度:1.8~18.0nm/min。
上記の特性を達成するため、EUV光の吸収係数が高い材料での構成が好ましく、タンタル(Ta)を主成分とする材料で形成されていることが好ましい。
さらに、本発明のEUVマスクブランクでは、吸収体層14に対して、吸収体層14の形成後に実施される加熱処理の際に、Mo/Si多層反射膜の最上層をなすSi膜の酸化を抑制するためのバリア層としての機能が求められる。
上述したバリア層としての機能を発揮するためには、吸収体層14は、酸素の拡散を防ぐために、結晶粒界が存在しないこと、すなわち、結晶状態がアモルファスであることが好ましく、Taおよび窒素(N)を含有するTaN層は、結晶状態がアモルファスの膜を形成しやすい点で好ましい。
吸収体層14として、上記した合計含有率でTaおよびNを含むTaN層において、TaとNとの含有率および組成比は下記の範囲を満たすことが好ましい。
Taの含有率 好ましくは10~95at%、より好ましくは60~90at%、
Nの含有率 好ましくは5~50at%、より好ましくは10~40at%、
TaとNとの組成比(Ta:N) 8:1~1:5。
吸収体層14としてTaN層を形成した場合、その結晶状態はアモルファスであり、表面の平滑性に優れている。具体的には、吸収体層14としてTaN層を形成した場合、吸収体層14表面の表面粗さ(rms)が0.5nm以下になる。
吸収体層14表面の表面粗さ(rms)が0.5nm以下であれば、吸収体層14表面が十分平滑であるため、エッジラフネスの影響によってパターンの寸法精度が悪化するおそれがない。吸収体層14表面の表面粗さ(rms)は、0.4nm以下がより好ましく、0.3nm以下がさらに好ましい。
ここで、反射層12上に保護層13を形成しない場合は、反射層12(具体的には、Mo/Si多層反射膜の最上層のSi膜)とのエッチング選択比が10以上を示す。
本明細書において、エッチング選択比は、下記式を用いて計算できる。
エッチング選択比=(吸収体層14のエッチング速度)/(保護層13(または反射層12)のエッチング速度)
エッチング選択比は、10以上が好ましく、11以上がさらに好ましく、12以上がさらに好ましい。
一方、吸収体層14の膜厚が大きすぎると、該吸収体層14に形成するパターンの精度が低下するおそれがあるため、100nm以下が好ましく、90nm以下がより好ましく、80nm以下がさらに好ましい。
吸収体層14としてTaN層を形成する場合、マグネトロンスパッタリング法を用いる場合には、Taターゲットを使用し、Arで希釈した窒素(N2)雰囲気中でターゲットを放電させることによって、TaN層を形成できる。
スパッタリングガス:ArとN2の混合ガス(N2ガス濃度は、3~80vol%、好ましくは5~30vol%、より好ましくは8~15vol%。ガス圧は、0.5×10-1Pa~10×10-1Pa、好ましくは0.5×10-1Pa~5×10-1Pa、より好ましくは0.5×10-1Pa~3×10-1Pa。)、
投入電力(各ターゲットについて):30~1000W、好ましくは50~750W、より好ましくは80~500W、
成膜速度:2.0~60nm/min、好ましくは3.5~45nm/min、より好ましくは5~30nm/min。
この加熱処理により、Mo/Si多層反射膜を構成する各層の構造緩和と界面のミキシングが促進される。そして、構造緩和とミキシングの促進により、Mo/Si多層反射膜の収縮により該Mo/Si多層反射膜の膜応力(即ち、圧縮応力)が緩和される。すなわち、Mo/Si多層反射膜での構造緩和とミキシングにより膜応力を緩和する、加熱処理の作用が発揮される。そして、膜応力の緩和により、基板の変形が緩和される。
また、構造緩和とミキシングの促進により、Mo/Si多層反射膜の応力の経時変化が抑制される。
この結果、多層反射膜での構造緩和とミキシングにより膜応力を緩和する、加熱処理による作用が最大限に発揮される。
また、Mo/Si多層反射膜の最上層のSi膜の酸化の抑制により、Mo/Si多層反射膜の反射特性の変化が抑制される。具体的には、EUV光照射時における反射光の反射率の低下が抑制される。
したがって、Mo/Si多層反射膜上に、RuまたはRu化合物で構成される保護層を形成した場合でも、該保護層上に吸収体層を形成する前に、加熱処理を施すと、保護層表面から拡散した酸素により、Mo/Si多層反射膜の最上層のSi膜が酸化されるおそれがあるので、該Si膜での膜応力(圧縮応力)の増加が懸念される。
また、該Si膜の酸化により、Mo/Si多層反射膜の反射特性の変化、具体的には、EUV光照射時における反射光の反射率の低下が懸念される。
さらにまた、加熱処理時に、保護層としてのRu膜やRu化合物膜の酸化により、これらの膜での膜応力(即ち、圧縮応力)の増加が懸念される。
また、これらの膜の酸化により、その光学定数が変化して、EUV光照射時の反射特性が変化するおそれがある。具体的には、EUV光照射時における反射光の反射率が低下するおそれがある。
本発明では、吸収体層がバリア層として機能することにより、保護層としてのRu膜やRu化合物膜の酸化や、保護層表面から拡散した酸素によるMo/Si多層反射膜の最上層のSi膜の酸化も抑制される。
これらの作用によっても、多層反射膜の膜応力を緩和する効果、および、多層反射膜の反射特性の変化を抑制する効果が発揮される。
一方、加熱処理温度が170℃よりも高いと、Mo/Si多層反射膜でのミキシングが進行しすぎて、多層反射膜の各層が大きく収縮し、EUV光照射時の反射特性の変化、具体的には、EUV光照射時における反射光の反射率が低下するおそれがある。加熱処理の温度は130℃~150℃がより好ましく、136℃~144℃がさらに好ましい。
また、加熱時間は、5~60分の範囲が好ましく、10~30分の範囲がより好ましい。加熱処理の時間が5分よりも短いと、Mo/Si多層反射膜での構造緩和とミキシングにより膜応力を緩和する、加熱処理の作用が不十分になるおそれがある。一方、加熱処理の時間が60分より長いと、ミキシングが進行しすぎて多層反射膜の各層が大きく収縮し、EUV光照射時の反射特性の変化、具体的には、EUV光照射時における反射光の反射率が低下するおそれがある。
なお、上記のように吸収体層表面に一定厚の表面酸化膜を形成する方法としては、大気雰囲気下の加熱処理に限らない。例えば、ヘリウム(He)、アルゴン(Ar)、ネオン(Ne)、クリプトン(Kr)、キセノン(Xe)のうち少なくともひとつを含む不活性ガスで希釈した酸素(O2)および窒素(N2)雰囲気中で加熱処理をしたり、酸素プラズマ中にさらした雰囲気中で加熱処理をしたりしてもよい。また、この方法で表面酸化膜を形成する場合であっても、その膜厚は、0.5~3nmが好ましく、1.5~2.5nmがより好ましい。
図2は、本発明のEUVマスクブランクの別の実施形態を示す概略断面図である。
図2に示すEUVマスクブランク1´では、吸収体層14上にマスクパターンの検査に使用する検査光における低反射層15が形成されている。
したがって、257nm程度の検査光の波長に対する保護層13表面(または反射層12表面)と吸収体層14表面との反射率の差が小さすぎると検査時のコントラストが悪くなり、正確な検査ができない場合がある。
以下、本明細書で検査光と言った場合、その波長を特に記載しない場合は波長257nmの光を指す。
図2に示すEUVマスクブランク1´のように、吸収体層14上に低反射層15を形成することにより、検査時のコントラストが良好となる。別の言い方をすると、検査光の波長での光線反射率が極めて低くなる。このような目的で形成する低反射層15は、検査光の波長領域(257nm近傍)の光線を照射した際の、該検査光の波長の最大光線反射率は、15%以下が好ましく、10%以下がより好ましく、5%以下がさらに好ましい。
低反射層15における検査光の波長の光線反射率が15%以下であれば、該検査時のコントラストが良好である。具体的には、保護層13表面(または反射層12表面)における検査光の波長の反射光と、低反射層15表面における検査光の波長の反射光と、のコントラストが、40%以上となる。
コントラスト(%)=((R2-R1)/(R2+R1))×100
ここで、検査光の波長におけるR2は保護層13表面(または反射層12表面)での反射率であり、R1は低反射層15表面での反射率である。なお、上記R1およびR2は、図2に示すEUVマスクブランク1´の吸収体層14および低反射層15にパターンを形成した状態で測定する。上記R2は、パターン形成によって吸収体層14および低反射層15が除去され、外部に露出した保護層13表面(または反射層12表面)で測定した値であり、R1はパターン形成によって除去されずに残った低反射層15表面で測定した値である。
本発明において、上記式で表されるコントラストは、45%以上がより好ましく、60%以上がさらに好ましく、70%以上が特に好ましい。
このような低反射層15の具体例としては、Ta、酸素(O)および窒素(N)を以下に述べる比率で含有するTaON層が挙げられる。
低反射層15として、TaON層を形成する場合、Ta、OおよびNの合計含有率は、60at%以上であることが好ましく、80at%以上がより好ましく、95at%以上がさらに好ましい。
低反射層15として、上記した合計含有率でTa、OおよびNを含むTaON層において、TaとOとNとの含有率および組成比は下記の範囲を満たすことが好ましい。
Taの含有率:20~80at%、好ましくは、20~70at%、より好ましくは20~60at%、
OおよびNの合計含有率:20~80at%、好ましくは30~80at%、より好ましくは40~80at%、
OとNとの組成(O:N):20:1~1:20、好ましくは18:1~1:18、より好ましくは15:1~1:15。
上記したように、エッジラフネスの影響によってパターンの寸法精度の悪化を防止するため、吸収体層14表面は平滑であることが要求される。低反射層15は、吸収体層14上に形成されるため、同様の理由から、その表面は平滑であることが要求される。
低反射層15表面の表面粗さ(rms)が0.5nm以下であれば、低反射層15表面が十分平滑であるため、エッジラフネスの影響によってパターンの寸法精度が悪化するおそれがない。低反射層15表面の表面粗さ(rms)は0.4nm以下がより好ましく、0.3nm以下がさらに好ましい。
スパッタリングガス:ArとO2とN2の混合ガス(O2ガス濃度5~80vol%、N2ガス濃度5~75vol%、好ましくはO2ガス濃度6~70vol%、N2ガス濃度6~35vol%、より好ましくはO2ガス濃度10~30vol%、N2ガス濃度10~30vol%。Arガス濃度5~90vol%、好ましくは10~88vol%、より好ましくは20~80vol%、
スパッタリングガスのガス圧:1.0×10-1Pa~50×10-1Pa、好ましくは1.0×10-1Pa~40×10-1Pa、より好ましくは1.0×10-1Pa~30×10-1Pa、
投入電力:30~1000W、好ましくは50~750W、より好ましくは80~500W、
成膜速度:0.1~50nm/min、好ましくは0.2~45nm/min、より好ましくは0.2~30nm/min。
なお、Ar以外の不活性ガスを使用する場合、その不活性ガスの濃度が上記したArガス濃度と同じ濃度範囲にするのが好ましい。また、複数種類の不活性ガスを使用する場合、不活性ガスの合計濃度を上記したArガス濃度と同じ濃度範囲にするのが好ましい。
そして、この場合においても、低反射層15の表面上に形成される表面酸化膜の膜厚は、0.5~3nmが好ましく、1.5~2.5nmがより好ましい。厚さが0.5nmより薄いと、吸収体層表面が十分に保護されず、洗浄に対する耐久性が低下するおそれがある。一方、厚さが3nmよりも厚いと、マスクパターンの検査光に対する最大光線反射率が大きくなり、そのコントラストが低下するおそれがある。例えば、低反射層15がTaONから構成される場合、低反射層形成後の加熱処理により形成される表面酸化膜は、酸素リッチのTaON、つまり、低反射層として構成されるTaONに対して、酸素(O)の組成が多い構成であり、この場合の低反射層TaONとは異なる構成の層として認識できる。具体的に、TaON上の表面酸化膜については、酸素の組成で識別が可能であって、低反射層となるTaON層に対して酸素が5at%以上の組成比となる層を表面酸化膜として特定できる。
高誘電性コーティングは、公知の成膜方法、例えば、マグネトロンスパッタリング法、イオンビームスパッタリング法といったスパッタリング法、CVD法、真空蒸着法、電解メッキ法を用いて形成できる。
(実施例1)
本実施例では、図1に示すEUVマスクブランク1を作製した。
成膜用の基板11として、SiO2-TiO2系のガラス基板(外形6インチ(152.4mm)角、厚さが6.3mm)を使用した。このガラス基板の熱膨張率は0.2×10-7/℃、ヤング率は67GPa、ポアソン比は0.17、比剛性は3.07×107m2/s2である。このガラス基板を研磨により、表面粗さ(rms)が0.15nm以下の平滑な表面と、100nm以下の平坦度に形成した。
平板形状をした通常の静電チャックに、上記の手順で形成されたCr膜を用いて基板11(外形6インチ(152.4mm)角、厚さ6.3mm)を固定して、該基板11の表面上にイオンビームスパッタ法を用いてMo膜およびSi膜を交互に成膜することを50周期繰り返すことにより、合計膜厚340nm((2.3nm+4.5nm)×50)のMo/Si多層反射膜(反射層12)を形成した。なお、Mo/Si多層反射膜の最上層はSi膜である。
[Mo膜の成膜条件]
ターゲット:Moターゲット、
スパッタリングガス:Arガス(ガス圧0.02Pa)、
電圧:700V、
成膜速度:3.84nm/min、
膜厚:2.3nm。
[Si膜の成膜条件]
ターゲット:Siターゲット(ホウ素ドープのSiターゲット)、
スパッタリングガス:Arガス(ガス圧0.02Pa)、
電圧:700V、
成膜速度:4.62nm/min、
膜厚:4.5nm。
保護層13の形成条件は、以下のとおりである。
ターゲット:Ruターゲット、
スパッタリングガス:Arガス(ガス圧0.02Pa)、
電圧:700V、
成膜速度:3.12nm/min、
膜厚:2.5nm。
TaN層を成膜条件は、以下のとおりである。
[TaN層の成膜条件]
ターゲット:Taターゲット、
スパッタリングガス:ArとN2の混合ガス(Ar:86vol%、N2:14vol%、ガス圧:0.3Pa)、
投入電力:150W、
成膜速度:7.2nm/min、
膜厚:60nm。
また、吸収体層14となるTaN層表面に、上記吸収体層14の加熱処理により形成された表面酸化膜、即ち、TaONの表面酸化膜について、Rigaku社製の高機能薄膜X線反射率膜厚測定装置を用いて、X線反射率測定法によりその膜厚を計測したところ、2nmであった。
本実施例では、図2に示すEUVマスクブランク1´を作製した。
本実施例におけるEUVマスクブランク1´のうち、基板11は実施例1と同じものを用い、さらに、基板11裏面側の高誘電性コーティングとなるCr層、Mo/Si多層反射膜(反射層12)、保護層13となるRu層および吸収体層14となるTaN層は、実施例1と同じ条件下で形成した。
TaON層の成膜条件は、以下のとおりである。
[TaON層の成膜条件]
ターゲット:Taターゲット、
スパッタリングガス:ArとO2およびN2の混合ガス(Ar:49vol%、O2:37vol%、N2:14vol%。ガス圧:0.3Pa)、
投入電力:250W、
成膜速度:2.0nm/min、
膜厚:8nm。
また、低反射層15となるTaON層表面に、上記低反射層15の加熱処理により形成された表面酸化膜について、Rigaku社製の高機能薄膜X線反射率膜厚測定装置を用いて、X線反射率測定法によりその膜厚を計測すると、約2nmとなる。
実施例1と同様の手順で保護層13まで形成した後、当該保護層13の形成後のEUVマスクブランクを大気雰囲気下、140±4℃の範囲内に制御して20分間加熱処理し、加熱処理後に吸収体層14を形成した。つまり、比較例1では、吸収体層14形成前の状態において、加熱処理を実施した。加熱処理実施前後の平坦度の測定については、保護層13の形成後に、加熱処理実施前の平坦度測定を行い、吸収体層14の形成後に、加熱処理実施後の平坦度測定を行った。
[実施例1のサンプル]
表面:0.217μm
裏面:0.237μm
[実施例2のサンプル]
表面:0.227μm
裏面:0.247μm
[比較例1のサンプル]
表面 0.195μm
裏面 0.192μm
加熱処理実施前後での平坦度の差分は、膜応力によって生じた基板11の反りが加熱処理によってどの程度緩和されたかを示している。両者から明らかなように、吸収体層形成後に加熱処理を行うことで、基板の反りを緩和する効果が向上した。
なお、2011年11月25日に出願された日本特許出願2011-257749号の明細書、特許請求の範囲、図面および要約書の全内容をここに引用し、本発明の開示として取り入れるものである。
11:基板
12:反射層(Mo/Si多層反射膜)
13:保護層
14:吸収体層
15:低反射層
Claims (17)
- 基板の成膜面上に、EUV光を反射する多層反射膜を形成した後、前記多層反射膜上にEUV光を吸収する吸収体層を形成することにより、EUVリソグラフィ用反射型マスクブランクを製造する、EUVL用反射型マスクブランクの製造方法であって、
前記多層反射膜が、Mo/Si多層反射膜であり、かつ、該Mo/Si多層反射膜の最上層がSi膜であり、
前記吸収体層の形成後、該吸収体層が形成された基板を110~170℃の温度で加熱処理するEUVリソグラフィ用反射型マスクブランクの製造方法。 - 前記吸収体層の形成後、該吸収体層が形成された基板を120~160℃の温度で加熱処理する、請求項1に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記多層反射膜の形成後、前記多層反射膜上に該多層反射膜の保護層を形成し、該保護層上に前記吸収体層を形成し、該吸収体層の形成後、該吸収体層が形成された基板に対し前記した加熱処理を施す、請求項1または請求項2に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記保護層が、Ru層、または、Ru化合物層である、請求項3に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記加熱処理を大気雰囲気下で実施する、請求項1~4のいずれか1項に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記吸収体層が、タンタル(Ta)および窒素(N)を合計含有率で60at%以上含有する層であり、かつ、前記吸収体層の膜厚が5~100nmである、請求項1~5のいずれか1項に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記加熱処理を実施して、前記吸収体層上に表面酸化膜を形成する、請求項1~6のいずれか1項に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 基板の成膜面上に、EUV光を反射する多層反射膜を形成した後、前記多層反射膜上にEUV光を吸収する吸収体層を形成し、前記吸収体層上にマスクパターンの検査に使用する検査光における低反射層を形成することにより、EUVリソグラフィ用反射型マスクブランクを製造する、EUVリソグラフィ用反射型マスクブランクの製造方法であって、
前記多層反射膜が、Mo/Si多層反射膜であり、かつ、該Mo/Si多層反射膜の最上層がSi膜であり、
前記低反射層の形成後、該低反射層が形成された基板を110~170℃の温度で加熱処理するEUVリソグラフィ用反射型マスクブランクの製造方法。 - 前記低反射層の形成後、該低反射層が形成された基板を120~160℃の温度で加熱処理する、請求項8に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記多層反射膜の形成後、前記多層反射膜上に該多層反射膜の保護層を形成し、該保護層上に前記吸収体層を形成し、該吸収体層上に前記低反射層を形成し、該低反射層の形成後、該低反射層が形成された基板に対し前記した加熱処理を施す、請求項8または請求項9に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記保護層が、Ru層、または、Ru化合物層である、請求項10に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記加熱処理を大気雰囲気下で実施する、請求項8~11のいずれか1項に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記吸収体層が、タンタル(Ta)および窒素(N)を合計含有率で60at%以上含有する層であり、かつ、前記吸収体層の膜厚が5~100nmである、請求項8~12のいずれか1項に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記低反射層が、タンタル(Ta)、酸素(O)および窒素(N)を合計含有率で60at%以上含有する層であり、かつ、前記低反射層の膜厚が1~30nmである、請求項8~13のいずれか1項に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 前記加熱処理を実施して、前記低反射層上に表面酸化膜を形成する、請求項8~14のいずれか1項に記載のEUVリソグラフィ用反射型マスクブランクの製造方法。
- 請求項7に記載のEUVリソグラフィ用反射型マスクブランクの製造方法によって得られる、吸収体層表面に膜厚0.5~3nmの表面酸化膜を有するEUVリソグラフィ用反射型マスクブランク。
- 請求項15に記載のEUVリソグラフィ用反射型マスクブランクの製造方法によって得られる、低反射層表面に膜厚0.5~3nmの表面酸化膜を有するEUVリソグラフィ用反射型マスクブランク。
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US14/227,523 Continuation US9423684B2 (en) | 2011-11-25 | 2014-03-27 | Reflective mask blank for EUV lithography and process for its production |
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JP (1) | JPWO2013077430A1 (ja) |
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JP2015008265A (ja) * | 2013-05-31 | 2015-01-15 | 旭硝子株式会社 | Euvリソグラフィ用反射型マスクブランク |
WO2015114043A1 (de) | 2014-01-30 | 2015-08-06 | Carl Zeiss Smt Gmbh | Verfahren zum herstellen eines spiegelelements |
DE102014201622A1 (de) | 2014-01-30 | 2015-08-20 | Carl Zeiss Smt Gmbh | Verfahren zum Herstellen eines Spiegelelements |
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DE102014219648A1 (de) | 2014-09-29 | 2015-10-15 | Carl Zeiss Smt Gmbh | Verfahren zum Herstellen eines Spiegelelements |
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JP2022087329A (ja) * | 2017-04-17 | 2022-06-09 | Agc株式会社 | Euv露光用反射型マスクブランク、および反射型マスク |
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Also Published As
Publication number | Publication date |
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TW201331699A (zh) | 2013-08-01 |
KR20140099226A (ko) | 2014-08-11 |
JPWO2013077430A1 (ja) | 2015-04-27 |
US20140212794A1 (en) | 2014-07-31 |
US9423684B2 (en) | 2016-08-23 |
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